The effective production of hydrocarbon reservoirs containing heavy oils or unconventional oils presents significant challenges. Extraction of these high viscosity hydrocarbons is difficult due to their relative immobility at reservoir temperature and pressure. These properties make it difficult to simply pump the unconventional oil out of the ground. Such hydrocarbons may be quite thick and have a consistency similar to that of peanut butter or cold molasses, making their extraction from reservoirs difficult.
Enhanced oil recovery processes employ thermal methods to improve the recovery of heavy oils from sub-surface reservoirs. The injection of steam into heavy oil bearing formations is a widely practiced enhanced oil recovery method. Typically, several metric tons of steam are required for each metric ton of oil recovered.
Traditionally, heavy oil recovery operations have utilized “once through” type steam generators. The steam or a steam-water mixture is injected via injection wells to fluidize the heavy oil. Different percentages of water and steam can be injected into the injection wells, depending on a variety of factors including the expected output of oil and the economics of injecting different water/steam mixtures. Steam heats the oil in the reservoir, which reduces the viscosity of the oil and allows the oil to flow to a collection well. After the steam fully condenses and mixes with the oil, the condensed steam is classified as produced water. The mixture of oil and produced water that flows to the production well is pumped to the surface. Oil is separated from the water by conventional processes employed in conventional oil recovery operations.
For economic and environmental reasons, it is desirable to recycle produced water. The produced water stream, after separation from the oil, is further de-oiled, and is treated for reuse. Most commonly, the water is sent to the “once-through” steam generators for creation of more steam for oil recovery operations.
Many patents and patent applications are directed to methods for treating produced water, including US20130248454, US20100264068, US20140151296. However, currently known and utilized methods for treating heavy oil field produced waters in order to generate high quality steam for down-hole are not entirely satisfactory because:                most physical chemical treatment systems are quite extensive, are relatively difficult to maintain, and require significant operator attention;        treatment systems require large amounts of expensive chemicals, many of which require special attention for safe handling, and which present safety hazards if mishandled; and,        a large quantity of unusable hot water is created, and the energy from such water must be recovered, as well as the water itself, in order to maintain an economic heat and material balance in operations.        
Many attempts have been made to overcome these issues. For instance, U.S. Pat. No. 8,656,999, by the Applicants, describes a treatment method that injects untreated produced water into a direct steam generator to generate a steam and an effluent stream with impurities that are combusted by the direct steam generator. While a step in the right direction, there is always a need for improved methods of treating produced water.
Thus, there exist a need for a quick and cost effect means of treating produced water for reuse or disposal. Ideally, the treatment will not require expensive equipment or treatment systems, require large amounts of chemicals, increase energy consumption or waste energy.